The present invention relates to a deflection apparatus, a cathode ray tube apparatus and a beam landing adjustment method which are applicable to a television receiver or a color monitor device and particularly facilitate an adjustment when installing the deflection apparatus in the cathode ray tube.
In a color television receiver and the like, because a deflection yoke is fitted onto a neck portion of a glass enclosure of the cathode ray tube (hereinafter referred to as CRT) against a funnel portion thereof to be fixed at a predetermined position. Each deflection yoke causes some unevenness in its deflection center if the deflection center of deflection yoke changes, the strike point of an electron beam on a fluorescent screen of a CRT will deviate. Due to the deviation of the strike point, color unevenness will be caused in a picture displayed on a CRT. For this reason, when a color television receiver is manufactured, specifically, the deflection yoke is manually moved for adjustment in the axial direction of the CRT so as to make the color unevenness minimum and then the deflection yoke is fixed on the glass enclosure. Adjusting to make the color unevenness minimum in this manner is termed xe2x80x9cBeam Landing Adjustmentxe2x80x9d or xe2x80x9cLanding Adjustmentxe2x80x9d. The deflection yoke is manually moved for adjustment in the axial direction of the neck portion.
With such manual adjustment, it takes much time to fix the deflection yoke in position where unevenness of color disappears, thus, a proposal to correct the deflection center of the deflection yoke electrically is disclosed e.g. in a publication of patent application No. H5-76018.
According to the above publication of patent application No. S52-71117, the following structure is disclosed. A first deflection yoke and a second deflection yoke are provided at a neck portion of a CRT. A sawtooth current synchronized with a horizontal deflection cycle and a vertical deflection cycle is made to flow in each coil of the second deflection yoke. By generating from the second deflection yoke a magnetic field inn the opposite direction to or the same direction as that of a magnetic field generated in the first deflection yoke, a position of the deflection center of the deflection yoke is electrically changed in the axial direction of the neck portion.
According to the above publication of patent application No. H5-76018, the following beam landing correction apparatus is disclosed. A velocity modulation coil is provided at the rear of the deflection yoke fitted onto the neck portion of the CRT. A sawtooth current is made to flow from a sawtooth current generator circuit provided in the receiver into the velocity modulation coil. The beam deflection center position of the deflection yoke is corrected by adjusting the amplitude and polarity of the sawtooth current of the current generator circuit.
According to the above publication of patent application No. S52-71117, it is disclosed that the second deflection yoke is formed by winding a horizontal deflection coil around an annular core to create a parallel magnetic field perpendicular to the axial direction of the neck portion and a horizontal sawtooth current synchronized with a horizontal deflection cycle is made to flow.
It is also disclosed that when the deflection center is to be advanced, the current of such a polarity as creates an opposite magnetic field to the horizontal deflection magnetic field generated by the first deflection yoke is made to flow, and when the deflection center is to be retreated, the current of the same polarity as that of the horizontal deflection magnetic field is made to flow.
However, how to adjust the amplitude and how to switch the polarity of the sawtooth current is not disclosed. Also, in the case of publication of patent application No. H5-76018, the sawtooth current similar to the above must be made to flow in the velocity modulation coil. In order to adjust the sawtooth current the adjustment of polarity and amplitude is required in the sawtooth current generator circuit. In other words, portion and the adjustment is performed, through an amplitude adjusting means and a polarity switching means of the sawtooth current generator circuit provided on the receiver side. Thus, the unevenness of deflection center of deflection yoke cannot be adjusted in a manufacture stage of the deflection yoke. Therefore, the adjustment for eliminating the color unevenness must be performed in a manufacture stage of color television receiver or the like. Thus, it takes much time to adjust, which leads to the increase in costs of manufacturing color television receiver.
The present invention has been made in order to solve the above described problem and is characterized by providing a landing correction coil near the deflection yoke and also providing an adjustment coil for adjusting the amplitude of the sawtooth current in a horizontal deflection cycle, which is made to flow in a landing correction coil. The present invention provides a deflection apparatus, making cathode ray tube apparatus and beam landing adjustment method capable of the beam landing adjustment to be performed more correctly and easily by the above-mentioned feature.
A first deflection apparatus according to the present invention comprises a landing correction coil and an adjustment coil for making a sawtooth current of a horizontal deflection cycle flow in the landing correction coil. This landing correction coil is provided near a horizontal deflection coil of deflection yoke and generated a magnetic field perpendicular to the axial direction of a neck portion of a CRT. The adjustment coil is connected in series with a horizontal deflection coil. The adjustment coil is made to be variable e.g. by a knob and the like. The sawtooth current of a horizontal deflection cycle made flow in the landing correction coil is variable by means of the knob.
A second deflection apparatus according to the present invention is such that, in the first apparatus, the adjustment coil is connected so as to form the bridge circuit, and first and second landing correction coils are connected in series between balance positions of the landing adjustment coil connected to form the bridge circuit.
A third deflection apparatus according to the present invention is such that, in the first apparatus, the landing adjustment coil has a first coil land a second coil connected in parallel with each other, and the landing correction coil is connected in series to either of the first coil and the second coil. The landing correction coil has a first coil and a second coil which are different from those described above and connected in series with each other.
A fourth deflection apparatus according to the present invention is such that, in any of the first to third apparatus, the landing adjustment coils are wound in symmetrical positions on a coil bobbin, and a knob for enabling a magnetic core such as a screw core arranged at the middle of the coil bobbin to move in and out of coils is provided.
A fifth deflection apparatus according to the present invention is such that, in any of the first to fourth apparatus, the landing adjustment coil is comprised of at least two coils and inductances of the at least two coils are differentially changed by moving the magnetic core such as the""screw core.
A sixth deflection apparatus according to the present invention is such that, in any of the first to fifth apparatus, the landing correction coil is arranged in the rear of (toward the neck) the horizontal deflection coil of the deflection yoke, i.e. on the neck side.
A seventh deflection apparatus according to the present invention is such that, in any of the first to fifth apparatus, the landing correction coil is provided within a magnetic field of the horizontal deflection coil of the deflection yoke.
A first cathode ray tube apparatus according to the present invention, comprises a deflection yoke, a landing correction coil and an adjustment coil. The deflection yoke is fitted on the neck portion of a CRT and is installed at a position where the yoke is pressed toward a funnel portion. The landing correction coil is provided at the rear of the horizontal deflection coil of the deflection yoke and generates a magnetic field perpendicular to the axial direction of the neck portion 10; a landing adjustment coil is connected in series with the horizontal deflection coil and used to make the sawtooth current of a horizontal deflection cycle flow in the landing correction coil 6. A varying means such as a knob is provided in the adjustment coil. It is possible to make variable of the sawtooth current of a horizontal deflection cycle flowing in the landing correction coil by means of the varying means.
A second cathode ray tube apparatus according to the present invention comprises a deflection yoke, a landing correction coil and an adjustment coil. The deflection yoke is fitted on the neck portion of the CRT and is installed at a position where the yoke is-pressed toward the funnel portion. A landing. correction coil is provided within a magnetic field of the horizontal deflection coil of the deflection yoke and generates a magnetic field perpendicular to the axial direction of the neck portion 10. The landing adjustment coil 7 is connected in series with the horizontal deflection coil and is used to make the horizontal sawtooth current 11 flow in the landing correction coil. A varying means such as an knob is provided at the adjustment coil. The varying-means can make variable the sawtooth current of the horizontal deflection cycle flowing in the landing correction coil.
A beam landing adjustment method according to the present invention is a method for adjusting electrically a deflection center position of the deflection yoke while fixing the deflection yoke installed in the CRT at a certain point. A landing correction coil is provided within a magnetic field of the horizontal deflection coil or at the rear of the horizontal deflection coil and generates a magnetic field perpendicular to the axial direction of the neck portion of the CRT by providing. The sawtooth current of a horizontal deflection cycle is made to flow in the landing correction coil through the horizontal deflection coil and a the adjustment coil. A varying means for varying the current made to flow in the landing correction coil is provided at the adjustment coil. According the adjustment coil enables the deflection center of the deflection yoke to move electrically in the back and forth direction of the neck portion. Accordingly, the beam landing can be adjusted electrically.
According to the deflection apparatus, the CRT apparatus and the beam landing adjustment method, the adjustment coil and the varying means are capable of adjusting the amplitude of the sawtooth current having the horizontal deflection cycle made to flow in the landing correction coil. This makes it possible to perform the delicate beam landing adjustment more correctly and easily. Therefore, a satisfactory beam landing characteristic can be obtained and a picture with less color unevenness can be displayed. Moreover, in constructing a television receiver, the deflection yoke can be fixed closely to a funnel of a CRT. This enables a deflection sensitivity of the electron beam to be improved and power consumption to be reduced. Furthermore, a long term variation of a mechanical fixed position of the deflection yoke will decrease. Thus, a spacer for fitting the deflection yoke and in turn an adhesive for fixing the deflection yoke spacer will be unnecessary.